This chapter highlights the common hematological alterations, including anemia, coagulopathy, thrombocytopenia, and systemic infection that might arise post-cardiac surgery. Anemia is often related to hemodilution, blood loss, or inadequate erythropoiesis, while coagulopathy results from the consumption of clotting factors, platelet dysfunction, or fibrinolysis. The systemic inflammatory response and transfusion of stored blood further worsen these changes. Advanced diagnostic tools like thromboelastography (TEG) and rotational thromboelastometry (ROTEM) have emerged as effective measures to guide blood product administration, reduce transfusion-related complications, and optimize outcomes. Evidence-based management, including restricted transfusion threshold, antifibrinolytic agents, and personalized anticoagulation protocols, are emphasized.